The food items of particular interest in the present invention are very heavy, dense materials such as intermediate, wet, cereal products prior to drying or other treatment such as puffing. The consistency of the products may be similar to that of oatmeal.
The type of apparatus of particular interest, in the present invention, is a holding or surge apparatus in the shape of a rectangular bin having a travelling conveyor or transport means forming the bottom of the bin to unload the same. One purpose of such holding or surge apparatus is to achieve tempering or equilibration of the product held in the bin. This comprises holding the product for a sufficient period of time to allow moisture migration from product of high moisture content to product of low moisture content to achieve moisture uniformity throughout the product.
Accordingly, the bin may be filled to a substantial depth, creating a heavy load on the transport or conveyor means forming the bottom of the bin. It is an object of the present invention to carry out the transport of product from the bed with as little frictional resistance as possible.
Another object of the present invention is to provide endless transport or conveyor means for the product in question which can be readily cleaned prior to recycle of any portion of said transport or conveyor means through the bin, e.g., the equilibration or tempering zone.
Prior U.S. Pat. No. 2,732,631, to Harold G. Black, assigned to assignee of the present invention, describes a conveyor-type dryer especially adapted for loose, fibrous or granular material comprising an endless conveyor having laterally spaced side chains supported on parallel side tracks for horizontal movement through a dryer. The conveyor is provided with vertical side guards disposed inwardly of the side chains, adapted to retain material on the conveyor. The side guards are in the form of a series of overlapping plates adapted to spread apart or separate to negotiate the turning radius at the conveyor end sprockets. The conveyor bed may be a foraminous support of wire mesh or perforated plates.
In the conveyor system of the U.S. Pat. No. 2,732,631 it is possible, even if the bed was of an air-impervious material, for product being conveyed to flow into cracks between the separate side plates and between the plates and conveyor bed, making it difficult to easily clean the conveyor. This is particularly the case when the material being conveyed is heavy, wet, material such as an intermediate cereal product.
It is also known to construct a conveyor bed of a rubberized belt material, and to run the belt between a pair of stationary parallel-spaced walls adapted to form the belt into a transitory trough. This is shown, by way of example, in prior U.S. Pat. No. 2,998,121 to N. W. Gilbert. Conventionally, the trough-forming means is adapted to simply bend the rubberized belt into a "U" shape. However, as noted in the U.S. Pat. No. 2,998,121, material can flow over the sides of such belts, creating a sanitary problem. This problem is purported to be solved in the U.S. Pat. No. 2,998,121 by providing longitudinally-extending hinge lines along the sides of the belt so as to permit forming the belt into a flattened-bottom shape, with vertical upstanding sides. However, in the apparatus of the U.S. Pat. No. 2,998,121 the problem exists, with heavy loads, that high frictional resistance is created between the belt sides and the forming means, particularly with heavy loads and a belt of substantial length. The high friction, in turn, has such adverse affects as high belt stress and traction problems at the drive roll.
In the U.S. Pat. No. 2,998,121, the central load carrying portion is supported by a plurality of spaced rollers, but under high loads, there is a tendency of the belt to form a catenary between the rolls, resulting in such difficulties as sealing the belt edges against the flow of material from the bed.
In prior U.S. Pat. No. 3,374,751 to C. R. Werner, the problem of frictional load resistance, with a moving, rubberized belt, is said to be overcome by introducing air into the space between the belt member and forming means for the belt. Such an apparatus is expensive to build and operate, and is not likely to function well with high loads.
Examples of other prior art conveying systems are contained in prior U.S. Pat. Nos. 2,746,171 to Fleming; 3,220,535 to Franklin et al; 3,331,490 to Daniels et al; and 4,067,318 to Flaith et al. All but the Daniels et al patent are assigned to assignee of the present invention. Also, it is known to vulcanize upstanding, vertical guards onto a flat rubber belt, to form a permanent configuration similar in cross-section to that of the U.S. Pat. No. 2,998,121 belt. However, conventionally, such belts are used for the transport of relatively light loads of material and are supported by a series of spaced rolls, or by a stationary bed on which the belt slides. The disadvantages of such supports were outlined above.